Conventionally, in the fields in which chemical resistance, corrosion resistance, biocompatibility, explosion proof property, light weight property, and heat retention are required, a resin screw using a resin as a material is sometimes used in case of carrying out a feeding operation and a fastening operation between articles
Because the resin screw has various kinds of characteristics but is weak in strength, as compared with a metal screw, application fields are limited. Therefore, the resin screw could not be used for an application field where the higher strength is required.
Patent Literature 1 (JP H07-293535A) discloses a resin screw in which fiber was mixed to improve tensile strength of the screw. In the resin screw disclosed in Patent Literature 1, long reinforcing fiber having the average fiber length of 0.3 mm or more is mixed in a thermoplastic resin, to enhance the binding and adhesion of the reinforcing fiber and the resin, and to improve the strength of the composite material.